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Rust musl build segfaults on startup when linked with LLD 12 #86712

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rocallahan opened this issue Jun 29, 2021 · 9 comments
Open

Rust musl build segfaults on startup when linked with LLD 12 #86712

rocallahan opened this issue Jun 29, 2021 · 9 comments
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@pnkfelix
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A-linkage Area: linking into static, shared libraries and binaries C-bug Category: This is a bug. E-needs-mcve Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example E-needs-test Call for participation: An issue has been fixed and does not reproduce, but no test has been added. O-musl Target: The musl libc P-high High priority regression-from-stable-to-stable Performance or correctness regression from one stable version to another. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@rocallahan
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Steps to reproduce:

$ git clone https://github.com/rocallahan/rust-musl-segfault.git
$ cd rust-musl-segfault
$ cargo +nightly build --target x86_64-unknown-linux-musl
...
$ target/x86_64-unknown-linux-musl/debug/test_crate
Segmentation fault (core dumped)

Since the code is literally

use nix::sys::stat::Mode;

fn main() {
}

I expected it to not segfault.
@rocallahan rocallahan added the C-bug Category: This is a bug. label Jun 29, 2021
@rocallahan
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$ ld --version
LLD 12.0.0 (compatible with GNU linkers)

If I actually use ld.bfd the problem goes away, so this is quite possibly an LLD bug, though it might not be.

@rocallahan
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The segfault is in musl's __libc_sigaction. The segfault is at this instruction:

=> 0x00007f844d139e29 <+142>:	mov    %eax,-0x4be2f(%rip)        # 0x7f844d0ee000

0x7f844d0ee000 is unmapped memory. Looks like a linker relocation points somewhere wild.

@rocallahan
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If I remove the use statement the problem goes away.

@12101111
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12101111 commented Jul 8, 2021

I can reproduce this issue, the output will segfault when

  1. use x86_64-unknown-linux-musl target
  2. crt-static is enabled -C target-feature=+crt-static (It enabled by default on musl )
  3. Use lld as linker ( Either use ld.lld directly -Clink-self-contained=yes -Clinker=ld.lld or use clang and linker args -Clink-self-contained=no -Clinker=clang -Clink-arg=-fuse-ld=bfd)
  4. In debug mode ( no --release or -Copt-level > 0 )

The bisect command is

export RUSTFLAGS="-Ctarget-feature=+crt-static -Clinker=clang -Clink-arg=-fuse-ld=lld"
cargo bisect-rustc --start 2020-08-07 --end 2020-08-09 -- run

The bisect result is:

get_commits_between returning commits, len: 13
  commit[0] 2020-08-07UTC: Auto merge of #75255 - davidtwco:polymorphisation-symbol-mangling-v0-upvar-closures, r=lcnr
  commit[1] 2020-08-07UTC: Auto merge of #75071 - ssomers:btree_cleanup_5, r=Mark-Simulacrum
  commit[2] 2020-08-08UTC: Auto merge of #75048 - eggyal:force-no-tco-start-backtrace-frame, r=Mark-Simulacrum
  commit[3] 2020-08-08UTC: Auto merge of #74877 - lcnr:min_const_generics, r=oli-obk
  commit[4] 2020-08-08UTC: Auto merge of #75276 - JohnTitor:rollup-rz4hs0w, r=JohnTitor
  commit[5] 2020-08-08UTC: Auto merge of #74932 - nnethercote:rm-ast-session-globals, r=petrochenkov
  commit[6] 2020-08-08UTC: Auto merge of #75257 - ssomers:btree_74762_again, r=Mark-Simulacrum
  commit[7] 2020-08-08UTC: Auto merge of #75282 - RalfJung:miri-black-box, r=oli-obk
  commit[8] 2020-08-08UTC: Auto merge of #74289 - lzutao:unroll, r=LukasKalbertodt
  commit[9] 2020-08-08UTC: Auto merge of #74533 - nikic:issue-74425, r=eddyb
  commit[10] 2020-08-08UTC: Auto merge of #75260 - davidtwco:polymorphization-promoted-substs, r=lcnr
  commit[11] 2020-08-08UTC: Auto merge of #75163 - canova:map_into_keys_values, r=dtolnay
  commit[12] 2020-08-08UTC: Auto merge of #75271 - cuviper:array-iter, r=LukasKalbertodt
ERROR: no CI builds available between 09f4c9f5082f78b0adcee83d3ab4337e000cd28e and ceedf1d5febd65b012b8bcd513d70a0a6a091210 within last 167 days

My environment:

> clang -v
clang version 12.0.0
Target: x86_64-gentoo-linux-musl
Thread model: posix
InstalledDir: /usr/lib/llvm/12/bin
> ld.lld --version
LLD 12.0.0 (compatible with GNU linkers)

@rustbot label: +A-linkage +O-musl +regression-from-stable-to-stable

@rustbot rustbot added A-linkage Area: linking into static, shared libraries and binaries O-musl Target: The musl libc regression-from-stable-to-stable Performance or correctness regression from one stable version to another. I-prioritize Issue: Indicates that prioritization has been requested for this issue. labels Jul 8, 2021
@apiraino
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thanks @12101111 for the additional information. Assigning priority as discussed in the Zulip thread of the Prioritization Working Group.

@rustbot label -I-prioritize +P-high +T-compiler

@rustbot rustbot added P-high High priority T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. and removed I-prioritize Issue: Indicates that prioritization has been requested for this issue. labels Jul 11, 2021
@pnkfelix pnkfelix self-assigned this Nov 18, 2022
@wesleywiser
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Testing with our build of lld 15 on nightly and this seems to work fine now:

$ rustc +nightly --version -v
rustc 1.67.0-nightly (77e57db38 2022-10-30)
binary: rustc
commit-hash: 77e57db384aca99444c3b5f6a9c86bc58a804d89
commit-date: 2022-10-30
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4
$ git clone https://github.com/rocallahan/rust-musl-segfault.git
$ cd rust-musl-segfault/
$ RUSTFLAGS="-Ctarget-feature=+crt-static -Clinker=rust-lld" cargo +nightly build --target x86_64-unknown-linux-musl
$ ./target/x86_64-unknown-linux-musl/debug/test_crate
$ echo $?
0

@pnkfelix
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Indeed, this seems it was "fixed" (or perhaps hidden) sometime in late August 2021:

% ND=nightly-2021-08-21 ; rustup update $ND ; rustup target add --toolchain $ND x86_64-unknown-linux-musl ; RUSTFLAGS="-Ctarget-feature=+crt-static -Clinker=rust-lld" cargo +$ND build --target x86_64-unknown-linux-musl && ./target/x86_64-unknown-linux-musl/debug/test_crate
info: syncing channel updates for 'nightly-2021-08-21-x86_64-unknown-linux-gnu'

  nightly-2021-08-21-x86_64-unknown-linux-gnu unchanged - rustc 1.56.0-nightly (a0035916e 2021-08-20)

info: checking for self-updates
info: component 'rust-std' for target 'x86_64-unknown-linux-musl' is up to date
   Compiling bitflags v1.2.1
   Compiling libc v0.2.97
   Compiling nix v0.17.0
   Compiling cfg-if v0.1.10
   Compiling void v1.0.2
   Compiling test_crate v0.1.0 (/media/pnkfelix/Rust/issue_86712/rust-musl-segfault)
warning: unused import: `nix::sys::stat::Mode`
 --> src/main.rs:1:5
  |
1 | use nix::sys::stat::Mode;
  |     ^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

warning: `test_crate` (bin "test_crate") generated 1 warning
    Finished dev [unoptimized + debuginfo] target(s) in 3.64s
Segmentation fault (core dumped)
15-15-24 issue_86712/rust-musl-segfault (git:main) [ERROR#139] % ND=nightly-2021-08-22 ; rustup update $ND ; rustup target add --toolchain $ND x86_64-unknown-linux-musl ; RUSTFLAGS="-Ctarget-feature=+crt-static -Clinker=rust-lld" cargo +$ND build --target x86_64-unknown-linux-musl && ./target/x86_64-unknown-linux-musl/debug/test_crate
info: syncing channel updates for 'nightly-2021-08-22-x86_64-unknown-linux-gnu'

  nightly-2021-08-22-x86_64-unknown-linux-gnu unchanged - rustc 1.56.0-nightly (d3e2578c3 2021-08-21)

info: checking for self-updates
info: component 'rust-std' for target 'x86_64-unknown-linux-musl' is up to date
   Compiling libc v0.2.97
   Compiling bitflags v1.2.1
   Compiling nix v0.17.0
   Compiling cfg-if v0.1.10
   Compiling void v1.0.2
   Compiling test_crate v0.1.0 (/media/pnkfelix/Rust/issue_86712/rust-musl-segfault)
warning: unused import: `nix::sys::stat::Mode`
 --> src/main.rs:1:5
  |
1 | use nix::sys::stat::Mode;
  |     ^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

warning: `test_crate` (bin "test_crate") generated 1 warning
    Finished dev [unoptimized + debuginfo] target(s) in 3.60s
%

@pnkfelix
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pnkfelix commented Dec 13, 2022 •
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I'm going to guess this was fixed by the LLVM 13 upgrade that took place with #87570 (on 2021-08-21).

@pnkfelix
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So I think the only thing that's blocking this ticket being closed is a regression test. Marking accordingly.

@rustbot label: E-needs-test

@rustbot rustbot added the E-needs-test Call for participation: An issue has been fixed and does not reproduce, but no test has been added. label Dec 13, 2022
@JohnTitor JohnTitor added the E-needs-mcve Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example label Dec 21, 2022
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@pnkfelix pnkfelix

Labels
A-linkage Area: linking into static, shared libraries and binaries C-bug Category: This is a bug. E-needs-mcve Call for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example E-needs-test Call for participation: An issue has been fixed and does not reproduce, but no test has been added. O-musl Target: The musl libc P-high High priority regression-from-stable-to-stable Performance or correctness regression from one stable version to another. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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@pnkfelix @rocallahan @wesleywiser @apiraino @12101111 @JohnTitor @rustbot